Prefabricated concrete products, such as hollow-core slabs and solid concrete slabs, are conventionally cast by slipform casting on long casting beds as a continuous casting process. The length of said continuous casting process is defined either on the basis of the total length of the elements to be cast, or on the basis of the maximum length of the casting bed. The length of casting beds used in slipform casting can be up to 150-200 m, depending on the size of the element plant. When a slipform casting equipment has cast a continuous slab on a casting bed, the cast concrete mass is allowed to be cured on the casting bed. After the concrete mass has cured, the uniform cast element is cut, generally by sawing, into pieces with predetermined lengths on the basis of the design characteristics of the ready-made elements, and the cut concrete elements are lifted off the casting bed to storage, to wait for transportation to their appointed targets of usage.
Several different slipform casting methods and devices are known in the art. The most common types of slipform casting methods for casting concrete products are extruder and slipformer methods. In the extruder method concrete mix is fed in a single feeding stage from a concrete mass container to feed screws which feed screws extrude the concrete mix to a slipform casting mold defined by upper surface of a casting bed and side and top plates of a casting machine. When casting hollow core slabs, the feed screws are followed by core forming mandrels forming the cores in form of longitudinal voids in the concrete product to cast. The compacting of the concrete product to be cast is achieved by vibrating and/or leveling motion of the side and top plates, and the forming of the cores is secured by back-and-forth compacting motion of an entity formed of the feed screw and the attached core mandrel. The casting machine moves along the casting bed driven by reaction force from the feed screws extruding the concrete mass and optionally with an additional drive motor. The ready cast product remains on the casting bed as the casting progresses. One known extruder-type casting machine and method are disclosed in publication EP 2 821 192, for example.
In the slipformer casting method concrete mix is fed at least in two feeding stages from a concrete mass container(s) to a slipform casting mold. In the first feeding stage concrete mass is fed to a lower portion of the casting mold formed by a top surface of a casting bed and side plates of a casting machine. The first feed stage of concrete mix is followed by vibrating shoes and core forming mandrels that by vibrating the concrete mix compacts the cast concrete mix and form the final shape of the lower part of the concrete product to be cast. In the second feeding stage concrete mix is fed onto the end portions of the core forming mandrels and on the previously cast concrete mix for casting the upper portion of the product to be cast, after which the concrete mix is compacted with a vibrating plate defining the upper surface of the slipform casting mold and located at the rear part of the casting machine. The ready cast product remains on the casting bed as the casting progresses.
Slipform casting is generally used for casting long products with uniform cross-section, such as massive or hollow core slabs, which are cut to predefined lengths after the cast concrete is cured.
The prefabricated slipform cast concrete products are often also provided with pre-tensioning strands, which provides additional strength, and thus increased loadbearing capability, to the concrete products. The slipform cast concrete products are generally used to form horizontal intermediate floor and similar structures in buildings. Slipform cast products can also be formed, in addition to hollow core or massive slabs, as poles, pillars and ribbed slabs, among others.
Different kinds of additional reinforcements and other items, such as lifting loop forming parts and welding plates, can be fixed to the pre-tensioning strands before casting, but this is often time-consuming, and the pressure of concrete mass, especially in extruder-type slipform casting, can move these parts. Thus many of these additional parts are added to the slipform cast concrete product after the casting manually or with different finishing machines.
Further, often the slipform casting mold restricts the addition of reinforcements and other parts to the pre-tensioning strands that extends from the outer surface of the slipform cast product. One solution for this problem is to use a sectional upper surface of the slipform casting mold, of which section can be arranged a suitable distance apart allowing reinforcements and other pieces to pass through the slipform casting mold and thus through whole slipform casting machine. this kind of solution is disclosed in publication EP 3 056 328.